The present invention relates to a linear motor for generating linear movement. More particularly, the present invention relates to a linear motor coil assembly having a plurality of coils arranged in a line in the direction of linear motion.
Machine tools are known that use a linear motor to cause a table to move linearly at high speed and to position the table with high precision. Recently, linear motors have become more widely used. Such motors do not a require conveying means such as a feed screw. A linear motor may be used in a machine tool when it is needed to generate a large thrust, and where more compact structures are needed. However, because of their compact size, linear motors generate more heat than rotary motors. The temperature rise associated with a linear motor may limit its rated thrust, and lower its mechanical positioning accuracy. In many cases, linear motors are encapsulated in a cover in order to prevent magnetic dust from infiltrating into the linear motor. Because of this encapsulation, insufficient natural cooling of the linear motor may result, making effective cooling of the linear motor an important consideration.
Japanese Laid-Open Patent Application 63-18956 discloses a cooling apparatus for a linear motor. The motor is equipped with a cooling tube at the bottom of a groove formed between adjoining pole teeth. This linear motor cooling tube will now be described in detail below with reference to FIG. 9, FIG. 10 and FIG. 11. A plurality of permanent magnets 3 having alternating magnetic poles are fixed in a line on the lower surface of a carrier 2 in the direction of movement. A fixed armature is made up of a plurality of T-shaped pole teeth 4, a base 5 connecting the pole teeth, and a coil 7 wound around the teeth 4. As clearly shown in FIG. 9, cooling tubes 8 are provided, one each at the bottom of grooves 6 formed by adjoining pole teeth 4. The cooling tubes 8 comprise, for example, a tube 8A which meanders around the grooves 6, as shown in FIG. 10. A coolant, in gas or liquid form, circulates in the pipe 8A. As shown in FIG. 11, the cooling tubes 8, may comprise stair-shaped pipes 8B. The pipes 8B are equipped with headers 8a and 8b which extend parallel to a moving direction, opposite with respect to the base 5, and a bridging section 8c, bridging the headers 8a and 8b. The coolant is introduced from one end of the header 8a, passes through the bridging section 8c and is discharged from one end of the header 8b. 
An object of the present invention is to provide a linear motor coil assembly that efficiently dissipates heat generated in the coil.
Another object of the present invention is to provide a compact linear motor coil assembly.
Still another object of the present invention is to provide a simple method of manufacturing a linear motor coil assembly, having a high cooling efficiency.
These and other objects are achieved by providing, according to the present invention, a linear motor coil assembly for developing linear motion. The coil assembly comprises a plurality of coils arranged in a line in the direction of movement, respective coil shafts being arranged perpendicular to the direction of movement, and a flat cooling pipe, having a cross section that is elongated in a direction parallel to the coil shafts and having folds into which the coils can be engaged, the cooling pipe meandering inside the plurality of coils.
The flat cooling pipe preferably has a plurality of clearance holes for passing coolant formed in a direction parallel to the coil shafts.
Alternatively, the flat cooling pipe for passing coolant may be formed by aligning and attaching a plurality of round pipes in a direction parallel to the coil shafts.
The flat cooling tube preferably has interleaved folds at least equal in number to the number of coils.
The linear motor coil assembly may also include cores, divided for each coil, around which the coils are wound.
According to the present invention, there is also provided a method of manufacturing a linear motor assembly for developing linear motion, comprising the steps of providing cores divided for each magnetic pole, winding coils around the respective cores, providing a flat cooling pipe having interleaved folds, at least equal in number to the number of coils, into which the coils may be engaged, fitting the core into the folds, and arranging the cores in a line on a base plate.
Other objects and novel features will become apparent upon consideration of the following description.